1. Field of the Invention
The present invention relates to a titanocene based compound having a carbonyl group, and a photosensitive composition used in the fields of printed wiring boards, lead frames, semiconductor packages, members for a display (e.g., color filters, pillar materials, rib materials, spacers, partition walls), three dimensional optical moldings, image forming materials (e.g., printing matrices, proofs) and pattern formation, using the titanocene based compound as a photopolymerization initiator, a photosensitive transfer sheet using the photosensitive composition, and a pattern forming method using the photosensitive transfer sheet.
2. Description of the Related Art
With highly advanced performances of photosensitive compositions, it is one of regards strongly required to make photosensitivity high. Among them, as a photopolymerization initiator having an absorbance in the range of long wavelengths, for example, a titanocene compound further having a substituent on a fluoroaryl group has been proposed (see European Patent Application Publication No. 12223, Japanese Patent Application Laid-Open (JP-A) No. 63-41483, JP-A No. 63-41484, JP-A No. 02-249, JP-A No. 02-291, JP-A 03-12403, JP-A No. 03-27393 and Summers L. et al., J. Am. Chem. Soc., 77:3604, 1955).
However, it is hard to say that the high photosensitivity has been sufficiently accomplished in the titanocene compound proposed above.
Meanwhile, as methods for synthesizing the titanocene compound linking an aromatic ring, the method employing (1) a step of preparing an aromatic lithium compound or an aromatic Grignard compound and (2) a step of reacting with a titanocene dihalide compound has been known (see Summers L. et al., J. Am. Chem. Soc., 77:3604, 1955).
However, there has been a problem in that the aromatic lithium compound or the aromatic Grignard compound can not be prepared from a raw material having a reactive functional group such as a carbonyl group.
Therefore, no titanocene based compound having the carbonyl group, no photosensitive compound whose sensitivity is enhanced by containing this as the photopolymerization initiator, no photosensitive transfer sheet using the photosensitive composition and no pattern forming method using the photosensitive transfer sheet have been provided yet, and it is an actual circumstance that further improvement and development are desired.